Composite structures typically comprise an absorbent core for an absorbent product which has an absorbent particulate material that is immobilized when wet. The absorbent core comprises a substrate layer with an absorbent material, such as an absorbent polymer material.
U.S. Pat. No. 4,863,076, issued on Sep. 5, 1989, discloses an apparatus and method for feeding particulate material from an aerated hopper into a process stream at a controlled flow rate. Whilst the flow rate of particulate material is controlled, this process is not capable of delivering a profiled distribution of the particulate material into the subsequent stage of the process.
EP-A-1 621 165, published Feb. 1, 2006, discloses a process for producing absorbent structures. The process comprises the steps of pre-metering an amount of particulate material by means of a transfer device having recesses on the surface which, in number, size and position, determine the pattern of particulate material taken up by the transfer device; moving the transfer device between a loading position and a meeting position; and expelling the particulate material onto a carrier layer at the meeting position so that a profiled distribution of particulate material is retained on the carrier layer. However, at ever-increasing process speeds, reliable and consistent transfer of the particulate material from the hopper into the recesses of the transfer device becomes difficult. In this case the recesses may not be consistently filled to the same level each and every time they are filled below the hopper and the accuracy and reproducibility of the profiled distribution on the carrier layer may be compromised.
There remains a need for a process and apparatus to accurately and reproducibly provide a profiled distribution of a particulate material, in particular and absorbent particulate material, to a carrier layer, even in a high speed process.